Geometry nodes - lock distributed position in animation
What version of Blender were you using for this as I get different results using 2.93.0 Alpha - I get a small number of particles popping in and out of existence as the surface moves but most of them stick with the surface as the ocean modifier distorts it. Also, I note that the Join Geometry node in your example has two separate input nodes but the 2.93.0 Alpha version has a single &quot;multi-input&quot; input node, showing you're likely on an earlier version.
Since the Geometry Nodes feature is still under development, I'd suggest re-trying with the latest version and seeing if this improves the situation.